Compare the value of money between two years with the CPI, or project today’s prices into the future.
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Enter an amount, the year it comes from and the year to compare it with: the calculator gives the amount with the same buying power, the total rise in prices and the average inflation a year. It uses the Consumer Prices Index (CPI) published by the Office for National Statistics, as calendar-year averages from 1988 to 2025. To look ahead instead, choose 'Project into the future' and a yearly inflation rate.
Enter the amount, the year it was paid or earned and the year to compare it with. Leave the second year blank to get the amount in 2025 pounds, the latest year published. It works both ways: £100 in 2025 expressed in 1990 pounds gives a smaller amount.
Enter an amount in today’s money, a yearly inflation rate and a number of years. You get what the same things would cost then if prices rose at that rate every year, and what the amount would then buy, in today’s money. The Bank of England’s 2% target is a common assumption; CPI inflation was 3.4% in 2025.
The calculator uses the CPI because it is the measure the Government uses to set the Bank of England’s inflation target. The CPI covers the whole United Kingdom, so the same figures apply in England, Scotland, Wales and Northern Ireland. The ONS publishes the annual averages to one decimal place, so a change over a single year can differ from the ONS headline annual rate by about 0.1 point: 2.61% against 2.5% for 2024. Amounts are rounded to the nearest penny, with halves rounded up.
The ONS CPI series starts in 1988, so this calculator does too. For earlier years, the Bank of England’s inflation calculator uses ONS estimates of the CPI from 1949, modelled on Retail Prices Index data, and the ONS Composite Price Index from 1750 to 1948; the Bank says such calculations are approximate and only a rough guide.
Amount in the end year = amount × CPI in the end year ÷ CPI in the start year.
Price rise = CPI in the later year ÷ CPI in the earlier year − 1, and average inflation a year = (that ratio)^(1 ÷ number of years) − 1.
Projection: future cost = amount × (1 + rate)^years; future buying power = amount ÷ (1 + rate)^years.
The CPI averaged 72.7 in 2000 and 138.4 in 2025, so £100 in 2000 is worth £100 × 138.4 ÷ 72.7 = £190.37 in 2025: prices rose by 90.37% over 25 years, or 2.61% a year on average. Over 2025 alone, £100 of 2024 became £100 × 138.4 ÷ 133.9 = £103.36, in line with the 3.4% annual rate the ONS published for 2025.
Divide the CPI of the end year by the CPI of the start year, and multiply the amount by the result. The Bank of England’s own calculator uses the same formula: cost in year B = cost in year A × price index in year B ÷ price index in year A.
It uses calendar-year averages, and the 2026 average will only be known once the ONS has published the December 2026 index, early in 2027. Meanwhile the ONS publishes the 12-month rate every month: CPI inflation was 3.5% in the year to September 2026.
The CPI is the measure the Government sets the Bank of England’s 2% target on, and the one the Bank’s inflation calculator uses. The ONS’s lead measure of inflation is the CPIH, which also includes owner occupiers’ housing costs.
It shows how much prices in general have changed, which is a useful benchmark when you weigh up a pay rise. A lease, a contract or a benefit that is index-linked states which index and which month to use, often a single month’s figure rather than a yearly average, so follow its terms.
Nobody knows future inflation. The Government has set the Bank of England a 2% target for CPI inflation, which makes 2% a common assumption, but CPI inflation was 3.4% in 2025 and 7.3% in 2023. Try a few rates to see the range.
This calculator gives general information, not legal, tax, financial or accounting advice. Its results are estimates based on average price changes and are not an official figure for a contract or any legal purpose.
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